U.S. Pat. No. 6,500,169 B1 discloses a handpiece for carrying out medical interventions. This handpiece contains a drive for a surgical tool that is to be fitted on the handpiece. An example of a surgical tool of this kind is an orthopedic shaver, with which material, for example tissue or bone material, can be removed inside a body during drilling or milling procedures. A membrane switch assembly is arranged on this known handpiece, with three actuation regions which are arranged in a row and are to be acted on manually and, upon manual actuation, act on switch elements and thus permit activation or control of the drive provided in the handpiece. The three actuation regions arranged in a row are formed on a plate-like, flexible keypad element. The keypad element is arranged covering a recess on the handpiece. A plate-like cover element positioned to engage over the keypad element is secured on the handpiece by a plurality of fastening screws and presses an outer edge area of the keypad element against an abutment surface of the handpiece in order to produce a fluid-tight seal.